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Burgess Shale discovery believed to be fossil record's first fish jaw

The Metaspriggina, which lived 505-million-years ago.
The two-inch creature is the latest organism discovered in the Burgess Shale fossil field, in the Canadian Rockies of British Columbia.
Handout/Calgary Sun/QMI Agency

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Researchers first clued into the find at Yoho National Park’s celebrated Burgess Shale a decade ago with the discovery of bits and fossilized pieces of what would later turn out to be a fish named metaspriggina.

Much clearer pieces of the embyonic jaw puzzle fell into place in 2012 with well-preserved traces of the 6-cm-long fish at what Jean-Bernard Caron praises as “the motherlode” of more recently-discovered fossil beds at Marble Canyon in Kootenay National Park.

“This is the first time we have a fossil that’s very close to the mark of the ancestral fish in our textbooks,” said Caron, a curator at the Royal Ontario Museum who was on the 2012 dig.

“It’s a real turning point in the evolution of vertebrates — it allowed the group to diversify and be successful and get to the top of the food chain.”

Finding fish fossils of the Cambrian era dating back 505 million years is an extreme rarity in Canada, said Caron.

The superb preservation of metaspriggina had opened a rare window, he added, to the ancestor of mammals, including humans.

“There are very large eyes, nostrils, a liver, maybe a heart — you can see yourself in it,” he said of the tadpole-like creature.

Also apparent in the fossils are structure in the ancient fish that allowed it to swim sideways as well as muscle bands much like those “that you can see in salmon,” said Caron.

There’s much more to be learned about the creatures and Caron and fellow researchers are confident they’ll do just that when they return next month for a 10-week stay of discovery at Marble Canyon.

“We only spent two weeks this this motherlode and only scratched the surface,” he said.

“Hopefully, we’ll discover new species of fish and many questions remain — do we have species better preserved that have fins?”

To protect its integrity, Parks Canada has restricted access to the Marble Canyon site.